In the field of molecular and diagnostic analysis, the ability to keep nucleic acids in a biological sample (and in particular, those contained in diagnostic samples obtained from human patients) stable, whether the specimen is taken in a remote field location, a doctor's office or in a laboratory, often determines whether the nucleic acids can be successfully analyzed. Nucleic acids in a biological sample quickly degrade and/or denature at room temperature and must generally be stored under freezing temperatures to remain stable; however, some degree of degradation still occurs over time. This problem is magnified when a specimen is collected at a remote field site, or a significant distance from a doctor's office or laboratory environment, and especially where there may be limited, or no, access to consistent and constant cooler/refrigerator/freezer conditions until the sample is analyzed, such as where access to electrical power, or refrigerator/freezer equipment is either unreliable, or non-existent. The problems associated with the collection and handling of biological specimens from which it is desirable to obtain nucleic acids are further exacerbated when the desired nucleic acids for downstream analysis include ribonucleic acid (RNA), which is particularly susceptible to degradation by endogenous or exogenous nuclease activity. Commercially-available specimen transport methods often use special transport media for biological samples for transport from point of collection to point of analysis, and in particular, packaging that imposes limitations on the time a sample may be stored, requires continual sample maintenance at low temperatures, even during transport or extended storage, and practically limits the time and distances possible between the collection site and the diagnostic laboratory.
In addition to concerns regarding specimen stability, there are often additional concerns regarding the handling and/or storage of reagents used in storing and transporting the collected samples. For example, the reagents themselves frequently require cold temperatures or other special care to maintain stability. Due to these stability issues, for example, transport of the reagents to a field site, storage at the field site before use, and transport of the biological specimens and reagents back to a testing site is a primary concern.
Another significant concern when working with biological specimens is the potential inoculation, release, or dissemination of live infectious pathogens or biological agents from the specimen into the environment. Specific protocols currently exist that are employed when handling samples that may be infectious or otherwise pose health or safety risks. If the sample is kept viable and/or biologically intact to preserve its integrity for testing, individuals involved in the collection, transfer, and testing process are potentially exposed to highly dangerous contagions. Additionally, innocent bystanders nearby a field or sample collection site (or nearby during transport) can be exposed if a release of the contagion occurs. As a result, the required safety measures typically increase the expense and effort required to move such samples from one location to another.
Until recently, clinical laboratory methods for pathogen detection were labor-intensive, expensive processes that required highly knowledgeable and expert scientists with specific experience. The majority of clinical diagnostic laboratories employed the use of traditional culturing methods that typically require 3 to 7 days for a viral culture—and even longer for some other bacterial targets. Furthermore, traditional culturing requires collection, transport, and laboratory propagation and handling of potentially infectious biological agents such as Ebola, avian influenza, severe acute respiratory syndrome (SARS), etc.
The field of clinical molecular diagnostics changed drastically with the advent of polymerase chain reaction (PCR) in the mid eighties, however, and shortly thereafter with real-time PCR in the mid 90's. Nucleic-acid based detection platforms employing e.g., quantitative real-time PCR (qPCR) or reverse transcriptase PCR (RT-PCR) and quantitative, real-time, reverse transcriptase PCR (qRT-PCR) assays can deliver results in hours versus days required for traditional culture and isolation methods making molecular detection methods the mainstay of modern diagnostic laboratory analysis. Recent improvements in detection chemistries, such as new and improved reporting/quenching fluors, minor groove binders (MGB) (TaqMan MGB™, Applied Biosystems; for a general reference, see also e.g., Baraldi et al., Pure Appl. Chem., 75 (2-3):187-194, 2003), and stabilized amplification reagents have paved the way for more sensitive and highly-specific nucleic acid detection assays, and have proved more timely, robust, and economical than antiquated cell culture-based methods. Advances in other nucleic acid detection strategies such as transcription-mediated amplification, ligase chain reaction (LCR), and so-called “laboratory-on-a-chip” multiplexed assays, have also contributed to the transition from culture vials to microarrays in the clinical laboratory.
Several commercial companies (e.g., Qiagen [Valencia, Calif., USA], Roche Applied Science [Indianapolis, Ind., USA], Gen-Probe [San Diego, Calif., USA], and bioMérieux [Durham, N.C., USA]) have developed instruments to automate the nucleic acid extraction process from sample isolation to molecular analysis. For example, the Tigris DTS® (Gen-Probe, San Diego, Calif., USA) automates the entire detection process, and in late 2004 was approved by the U.S. Food and Drug Administration (FDA) for simultaneously detecting Chlamydia trachomatis and Neisseria gonorrhoeae using Gen-Probe's APTIMA COMBO-2® amplified nucleic acid test (NAT) assay.
In view of the requirement for high-quality nucleic acid samples in contemporary detection and assay systems, there is now a need in the art for safe and facile collection, storage and transport systems that maintain the integrity and quality of nucleic acids contained within a variety of biological samples and specimens. Moreover, there is also now a need for collecting, preserving, and transporting samples (and particularly those containing harmful or pathogenic organisms) in remote or field locations under ambient environmental (i.e., non-ideal) conditions for extended periods of time without refrigerating, freezing, or otherwise special handling of the collection reagent(s), the biological sample itself, or the population of nucleic acids contained therein. Furthermore, there is now a need for less-expensive, and more-convenient collection/transport/storage media that minimize risk of pathogen exposure to workers or innocent bystanders, allow for the use of single-step formulations, and facilitate convenient ambient transportation of biological specimens over long distances or extended periods of time that contain high-fidelity, high-quality nucleic acid populations.